Field of the Invention
The present invention relates to a lens barrel and an image pickup apparatus having the lens barrel.
Description of the Related Art
A digital camera is provided with a zoom mechanism for changing image pickup magnification by a lens barrel having a plurality of lenses. The lens barrel is assembled by assembling a plurality of cam barrels in order from an object side in an optical axis direction and mounting a sensor holder from an image pickup device side in the optical axis direction last.
In this regard, each of the cam barrels and lens groups is assembled against a cam groove by a cam in an assembling phase area on the image pickup device side in the optical axis direction, the assembling phase area being nearer to the image pickup device than the end of the storage space of the cam barrel. The cam is rotated to the object side in the optical axis direction a little from the end of the storage space of the cam barrel, and the sensor holder as a stopper is provided so that the cam barrel does not rotate upto the assembling phase area (see Japanese Laid-Open Patent Publication (Kokai) No. 2007-4030, for example).
However, the lens barrel assembled by mounting the sensor holder is not capable of adjusting the optical lenses inside the lens barrel after the sensor holder has been mounted. For this reason, in the case of desiring to adjust the optical lenses while assembling the lens barrel, it is not possible to advance to the assembly work after the sensor holder has been mounted.
In the recent digital camera market, it is required to provide a lens barrel capable of high-magnification zooming with the downsizing promoted. That is, it is necessary to improve the sensitivity of a lens group, positioned on the object side in the optical axis direction at the time of performing image pickup, among lens groups disposed in a digital camera, and to accurately determine a lens position.
Such a lens barrel is provided with a fixed cam ring, a movable cam ring having a plurality of lens groups built-in and received in the fixed cam ring, and an external barrel unit fixed to the mobile cam ring. In order to accurately perform positioning of lenses, it is desirable to mount the external barrel unit of the lens barrel from the object side in the optical axis direction after having performed lens adjustment from the object side in the optical axis direction. Furthermore, it is desirable that the external barrel unit is removable so that positioning of the lenses can be performed again after the external barrel unit having been mounted, which may, however, cause the external barrel unit to unexpectedly come off during a time period after the mounting until the removal.